On its 60th anniversary, the Korean War looks much like Vietnam, a pointless conflict that gained nothing for those who began it: North Korea’s Kim Il-sung and South Korea’s Syngman Rhee, with the consent of the Soviet Union’s Joseph Stalin and China’s Mao Zedong. Yet it was far worse than that: The bloodletting in that corner of northeast Asia was an exercise in human folly that cost all sides in the fighting nearly 4 million lives lost, missing, and wounded, not to mention the devastation of the peninsula from Pusan in the south to the Yalu River in the north. Not a single northern or southern Korean city escaped the ravages wrought by modern warfare. Public buildings and private homes were turned into piles of rubble, while thousands of refugees fled from the scenes of battle.

Despite a monument to its fallen heroes and considerable retrospective praise of Harry Truman for standing up to communism, America’s leaders—the president, Secretary of State Dean Acheson, Far Eastern Commander Douglas MacArthur, and Republican Sen. Joseph McCarthy—cannot lay claim to much, if any, praise for their parts in the conflict. As America wrestles with the wars in Iraq and Afghanistan and debates how to end U.S. involvement, the Korean War may be a useful cautionary tale—a reminder of how false assumptions about the benefits of military action can be so costly and unproductive and how political pressure to satisfy demands for military steps against perceived enemies can be worse than inaction.

By June 1950, anyone focusing closely on events of the previous two to five years should not have been surprised that a Korean civil war was in the offing. The governments of both the North and the South stridently proclaimed their determination to unify the country under their respective regimes.

In the North, Kim Il-sung was a 38-year-old firebrand. In 1929, as a 17-year-old student in Manchuria, where he and his family had moved to escape the oppressive Japanese occupation, he had joined the Communist Party. Between 1930 and 1945, he moved back and forth between China and Russia, distinguishing himself in the eyes of communists in both countries as a commander of Korean troops fighting the Japanese. His devotion both to Korean independence from Japanese imperialism and to Marxist doctrines made him an attractive choice to head the provisional government in Pyongyang, where he reflected Moscow’s determination to impose a communist government on all of Korea.

In 1948, after the Soviets rejected calls for UN-supervised elections as a prelude to Korean unification, Moscow rewarded Kim’s loyalty by making him the leader of the Korean People’s Republic, implying that he should be recognized as the governing authority for all of Korea. It was the first step in Kim’s attempt to make himself the ultimate ruler of the whole peninsula, if possible, or at least the all-powerful leader of a North Korean state.

Although his ambition to govern all Korea would be frustrated, he succeeded beyond anything Stalin and Mao—two of the most storied tyrants of the 20th century—achieved as authoritarian heads of their parties and peoples. Kim elevated himself to transcendent sovereignty over the North, creating a cult of personality comparable only to that of a religious figure. Monuments to the “Eternal President,” as the country’s constitution described him, made Kim an omni-present figure in every city and hamlet. His adoring compatriots paid homage to him at a 66-foot bronze statue of the Great Leader in Pyongyang.

Like the other ruthlessly authoritarian figures of his generation—Hitler, Stalin, Mao—Kim created a military arm that could defend his government from internal and external threats and reach across his borders to satisfy imperial ambitions. By 1950 his Soviet-supplied armies were prepared to counter any attack from the South or to move across the 38th parallel to bring all of Korea under his control.

Kim’s concern that South Korea might attack before he struck was not simply paranoid speculation. From his election as president of South Korea in 1948, Syngman Rhee had urged a “march north” to rid the peninsula of communist influence and achieve his lifelong dream of ruling a single Korean nation.

Like Kim, Rhee had spent most of his life in exile, returning home at age 70. He burned with urgency to unify Korea and believed that the hardships he had endured as a nationalist abroad entitled him to the presidency of a modern Korean state. In his 20s he had spent seven years in prison for opposing Japanese rule. Upon his release, he traveled to the United States, where he studied at George Washington University, Harvard, and Princeton, earning a Ph.D. in international law at the latter institution. Returning to Korea for three years between 1910 and 1913, he renewed his political opposition to Japanese colonialism, which obliged him to settle in Hawaii as the principal of a Korean school.

In 1919 Rhee was elected president of a provisional Korean government formed by pro-independence factions based in Shanghai. Unable to assert himself effectively over the divisive groups that made up the nominal coalition, he was ousted in 1925 amid charges of abuse of power. Rhee’s dictatorial tendencies would eventually find full flower when he became South Korea’s first president in 1948. After 1945, extreme fragmentation had marked South Korean politics: 205 groups asked for recognition as separate political parties, prompting one weary member of the U.S. occupying forces to jest that “Every time two Koreans sit down to eat they form a new political party.” Rhee would meet this factionalization by exercizing ruthless unitary power.

Rhee’s campaign to remove all leftists from political influence, in addition to such unconstitutional actions as arbitrary arrests, detentions, and torture of opponents, soon provoked nationwide anger that swelled into armed resistance. Observing this, Kim believed that should his armies cross the parallel, they would be welcomed as liberators.

It was the Truman administration’s misfortune to have two such overbearingly self-righteous figures vying for power over Korea. Their parallel pursuit of despotic unification left little room indeed for any genuine consideration of the well-being of the Korean people. Each considered bloodshed and unconstrained repression a small price to pay for fulfilling his dreams of becoming the founder of a modern Korean nation. With such leaders, the Korean people needed no foreign occupiers to abuse them. But full-scale war broke out on June 25, 1950, only as the consequence of an extraordinary combination of events and judgments in at least five countries: North and South Korea, the Soviet Union, China, and the United States.

In 1949 Rhee’s government had initiated a series of attacks upon the North Korean forces stationed along the 38th parallel. Because he lacked sufficient troops and equipment to launch a serious push north, Rhee provoked the fighting not only to command Washington’s attention and stimulate an outpouring of military and financial aid but also to provide a pretext for cracking down on leftist opponents.

Rhee’s success against the leftists, along with his developing relationship with Japan that promised to strengthen South Korea’s economy, prompted Kim to step up his plans to strike the South. In 1949 Kim had pressed Stalin for permission to invade the South. But the Soviet dictator had equivocated, urging Kim instead to support the insurgencies. At the beginning of 1950, however, Stalin’s opposition had softened, due in part to the Soviets’ acquisition of the atomic bomb, Mao’s victory in China, an emerging alliance with Peking, and the conviction that Washington would shortly reach a peace agreement with Tokyo that would station U.S. forces in Japan indefinitely and threaten Moscow’s Far East possessions. An East–West standoff in Europe had shifted Stalin’s focus to Asia, where opportunities for communist gains seemed greater. Secretary of State Acheson’s description of a Northeast Asian defense perimeter in January 1950 seemed to confirm Stalin’s belief that the United States would not interfere in Korea, a factor that he believed left South Korea open to an unchallenged attack from the North.

Stalin also saw little downside should America reverse course and intervene in Korea. He believed that U.S. involvement in the peninsula would reduce the threat to Soviet forces in Germany and to Moscow’s control of Eastern Europe. A drawn-out conflict that eventually pitted China against the United States would further “distract the United States from Europe to the Far East,” wrote Stalin to Czechoslovakian President Klement Gottwald in an August 1950 cable. “And the third world war will be postponed for the indefinite term, and this would give the time necessary to consolidate socialism in Europe.” It also gave the Soviets time to develop a hydrogen bomb, for which their spy Klaus Fuchs, whom the Soviets playfully called “Santa Klaus,” had secretly passed them the American design Edward Teller had developed in 1946.

Yet Stalin would not sanction the attack unless Kim sought Mao’s support before he acted. It was possible that the Chinese would oppose a war on the peninsula out of concern that it could bring U.S. intervention, the defeat of Kim’s regime, and the establishment of a dangerous pressure point against the Bejing government, developments that would reverse Moscow’s apparent triumphs in Asia.

But the Chinese did not resist Kim’s war plans. Like Kim and Stalin, Mao doubted that the Americans would fight to prevent unification of the peninsula. Communist convictions that South Korea would be abandoned by its sponsor were reinforced in May 1950, when Tom Connally, the chairman of the Senate Foreign Relations Committee and a Democratic ally of Truman, publicly acknowledged that the United States probably could not stop a communist takeover in Seoul. Not long after, Acheson reiterated the administration’s Korean policy, brushing aside suggestions that the United States would intervene.

Although the Chinese would have preferred to oust Chiang Kai-shek’s Nationalists from Taiwan before war broke out in Korea, they could not deny Kim’s request for moral and materiel backing, as well as a commitment to join in should U.S. forces threaten Pyongyang. Saying no would have made the Chinese seem less revolutionarily zealous than the USSR, with which they already had a keen, if muted, rivalry. Moreover, a sense of obligation to North Korea’s communists, who had fought under Mao against Chiang, made it difficult for Peking to discourage Kim from fighting his own civil war.

In the final analysis, the war was the result of misjudgments by the heads of government in Pyongyang, Moscow, Peking, Seoul, and Washington, none of whose calculations proved prescient. If Stalin, Mao, and Kim had had a better understanding of the political pressures on the Truman administration, they would have more realistically judged the likelihood of U.S. intervention. If Truman and Acheson had anticipated the irresistible pressure that the United States would feel to intervene, they would have openly guaranteed support for Seoul against any attack and warned North Korea not to test America’s resolve.

The various despots involved operated with a casualness about potential war costs that set them apart from the Truman administration. The two Koreas, China, and the Soviet Union were never as put off by the prospect of a civil war as was Washington. Kim, Rhee, and Mao rationalized their actions as serving various greater goods that transcended a few million deaths; when the results of their policies brought unspeakable suffering, they lauded these sacrifices as the cost necessary to bring about their peoples’ long-term well-being. Stalin could feel less troubled about a Korean outbreak than Peking, Pyongyang, or Seoul because he would not commit Soviet troops to the fighting. The deaths of Koreans, Chinese, and Americans in the conflict he had authorized weighed little on him. Having shed so much Soviet blood by mistakenly aligning himself with Hitler in 1939, and having previously crushed all real and perceived opposition to his rule, he was indifferent to having others die in the pursuit of what he believed would serve his country and enhance his personal power. Later, as the Korean conflict dragged on and casualty rates soared, Stalin would observe that the North Koreans “lose nothing, except for their men.”

The news that Kim had finally made his move shocked official Washington, not because a Korean civil war had seemed so unlikely but because a defeated South Korea would undermine America’s international position and public confidence at home. Truman’s decision to resist the attack with U.S. forces was no surprise. A failure to respond, he believed, would be comparable to the Anglo-French appeasement of Hitler at Munich in 1938. He knew that the Soviets had inspired North Korea’s aggression; if unresisted, other communist offensives in Europe and Asia would soon come.

Truman did not openly acknowledge how much domestic politics influenced his decision. When Under Secretary of State James Webb asked to discuss the political aspects of the situation at a White House conference, Truman replied, “We’re not going to talk about politics. I’ll handle the political affairs.” The president himself would deal with domestic pressure on the right from the likes of Sen. Joseph McCarthy, who would pillory the administration if it let South Korea fall.

Not only Republicans were eager for a strong response: in the spring of 1950, communist advances in the cold war had dropped the president’s approval rating to 37 percent. America’s eagerness for strong military leadership was evident in a 1952 presidential poll in which Gen. Dwight Eisenhower earned 60 percent, Truman 31. Once the president deployed troops to Korea, 65 percent of the respondents in a survey applauded the decision, even though 57 percent believed that World War III had begun.

By not acknowledging that domestic politics had played a role in his decision, Truman was reluctant to concede that he had acted to counter complaints about “losing” China and “allowing” Soviet spies to steal atomic secrets. Yet he understood that another cold war setback could decisively cripple his capacity to govern 18 months into his elected term. To be sure, Truman and Acheson believed it essential to stand up to aggression were they to avert world war. Countering Kim’s attack and blocking Mao from invading Taiwan would sustain a balance of power in the Far East and convince European allies that the United States would defend them against aggression. For Truman to maintain effective governing authority during the remaining two and half years of his presidency, it would be essential to assuage the country’s anxiety about the communist threat by meeting it head-on in Korea and the Taiwan Strait.

However popular the administration’s response to the invasion, it did not excuse Truman and Acheson’s failure to forestall it by making clear that South Korea could not be forced within a totalitarian sphere. America’s inattentiveness to developments on the peninsula had licensed the communist attack. And while no one should palliate the communists’ prime responsibility for the fighting, Washington’s overt avoidance of the Korean question before June 1950 contributed to the conditions that led to war.

To downplay the fear that the world was teetering on the brink of a worldwide conflict, Truman sensibly described America’s military intervention as a “police action” under the auspices of the United Nations. His decision, however, had adverse long-term consequences. By committing forces to fight in Korea without congressional authorization, he set a precedent for the unilateral presidential decisions that Lyndon Johnson, Richard Nixon, and George W. Bush would use to fight in Vietnam (1964), Cambodia (1970), and Iraq (2003). While presidents had sent troops into combat without congressional authorization before 1950—the State Department sent Truman a memo listing 87 such instances—they had typically been limited forays to protect and remove U.S. citizens from war zones.

Because Congress never speaks with one voice, it is vulnerable to the “imperial presidency” in times of crisis. Nevertheless, the legislature’s 1950 failure to assert itself more forcefully against the executive’s preemption of its war-making power was an invitation to future presidents to fight without the democratic debate that the founders of the Republic considered essential. The Korea, Vietnam, and Iraq conflicts should serve as cautionary tales about what happens when robust debate does not take place within and between the two branches of government that are responsible for the decision to make war.

In the Soviet Union, Stalin understood that the Korean fighting could serve him domestically as well—as a valuable tool for suppressing his domestic opponents, the men and women in his inner circle whom he saw as angling to replace him, and the ethnic groups he believed were intent on subverting his rule. Sending them to exile in the gulags would prove far easier if external dangers continued to make him the country’s indispensable leader, as World War II had done. It is a universal truth, wrote James Madison prophetically, “that the loss of liberty at home is to be charged to provisions against danger, real or pretended, from abroad.”

In September 1950 Stalin’s assumptions about what Moscow might gain from U.S. involvement in Korea fell victim to a brilliant American campaign that drove the invaders back across the 38th parallel. Suddenly the destruction of Kim’s regime and the incorporation of the North into one united country legitimized under the authority of the United Nations mandate seemed within reach.

After an October meeting during which Gen. Douglas MacArthur predicted an easy victory without Chinese intervention, Truman agreed to a conclusive invasion of the North. Truman had doubts that MacArthur’s scenario would play out, but domestic politics still loomed large in his thinking. To have stopped at the parallel would have brought a firestorm of criticism from right-wing politicians, who would charge that his containment policy was no prescription for cold war victory but rather a formula for defeat.

Once America threatened to establish, as they saw it, a garrisoned client state on the peninsula, the Chinese felt compelled to enter the conflict. They hoped not only to prevent an American military presence on their Manchurian border, save Kim’s ideologically acceptable regime, and inspire Third World revolutionaries in general to continue the struggle against Western imperialism, but further to energize one more domestic campaign to suppress “reactionaries and reactionary activities.”

The Korean War now became a toxic brew for everyone who supported it. None of the participating nations would escape the consequences of prolonged war on the peninsula. Two and a half more years of bloodshed gained nothing for any of the combatants. The Koreans, who suffered 3 million casualties, ended the war essentially where it had begun—more or less along the 38th parallel. Neither side was able to end the divide between North and South; each was left to govern not a unified Korea, which each had sought, but shattered individual nations more deeply antagonistic to one another than before. Although the Chinese took some comfort in their belief that they had frustrated the U.S. attempt to occupy Korea and use it as a forward base against their new revolutionary order, they had lost as many as 900,000 lives and embittered relations with America, delaying the day when they could use the United States to help build their economy and enlist it as an ally of sorts in its emerging conflict with the Soviet Union. As for Moscow, instead of limiting the U.S. ability to build its worldwide defenses by tying it down in an Asian land war, the Korean conflict spurred a worldwide American defense buildup that in due course forced the Soviets into a frenzied military counterexpansion its economy could not sustain.

In America, the extended bloodletting in Korea caused the political collapse of the Truman administration. By January 1951, 49 percent of Americans believed that U.S. participation in the war was a mistake, and only 38 percent endorsed it. Truman’s approval rating plummeted to 26 percent in February 1951. Political opponents joked, “To err is Truman.”

Douglas MacArthur’s intemperate demands to expand the war against China brought an end to his great career. He urged the United States to drop 34 atomic bombs on Manchuria, creating a 60-year radioactive belt against further invasion of Korea from the north. Truman wisely dismissed the general.